Breech end section of lined gun barrel



United States Patent [72] Inventor George H. Keith East Orange, NJ.

{21] Appl. No. 532,128

{22] Filed Sept. 1, 1955 Dec. 29, 1970 United States of America as represented by the Secretary of the Army. by mesne assignment [45] Patented [73] Assignee [54] BREECH END SECTION OF LINED GUN 1 Claim, 3 Drawing Figs.

[52] US. Cl. 89/16, 29/1. 1 1. [51] Int. Cl F411 17/08 [50] Field otSeai-ch 89/ 16;

Primary Examiner-Benjamin A. Borchelt Assistant ExaminerStephen C. Bentley A!torne \-sHarry M. Saragovitz, Edward J. Kelly and Herbert Berl ABSTRACT: In a lined gun barrel having a longitudinal bore and tenninating at its breech end in a reduced coaxial externally threaded portion defining a rearwardly facing peripheral shoulder, a barrel liner comprising a continuous tube of identical composite rings concentrically joined in end to end relation to form a continuous tube having a smooth longitudinal bore. said tube adapted to be inserted in said longitudinal bore of said barrel to a distance whereby a portion equal to substantially one half the length of one of said rings extends rearwardly of said gun barrel, each said ring including an outer ring of steel and an inner ring of molybdenum alloy, an end cap for said tube defining an enlarged forward portion and a reduced rearward portion forming a rearwardly facing shoulder, said forward portion having an enlarged bore equal in diameter to the external diameter of said barrel liner tube and an axial dimension equal to said extending portion of said liner, said rearward portion having a reduced bore equal in diameter to the inner diameter of said rings, and means locking said end cap to said liner in said bore in said gun barrel comprising an internally threaded sleeve terminating in an annular internal flange of the same diameter as said external diameter of said reduced portion of said end cap, said sleeve when threaded on said threaded reduced portion of said gun barrel to abut said rearwardly facing shoulder on said barrel and form a smooth peripheral surface therewith and said flange to abut said rearwardly facing shoulder on said end cap and lock said end cap in abutting relation to said liner.

BREECH END SECTION OF LINED GUN BARREL This invention relates to a gun barrel of the type having a rifled liner of hard metal such as molybdenum or molybdenum alloy, and to the method of constructing such a barrel.

The present invention relates to a special purpose type gun barrel which has no cartridge chamber. The projectile and cartridge rest in chambers provided in a revolving drum. This drum is disposed snugly against the breech'end of the barrel. As the drum revolves and each chamber aligns with the barrel the cartridge is fired and the projectile proceeds down the bare barrel.

The barrel is rifled. There is a length of barrel between the origin of rifling and the breech end thereof which is subjected to the gases of propulsion and other stresses concomitant with firing. This section is lined with a mu molybdenum liner since it is better able to withstand the forces of erosion and corroslon.

In prior art gun barrels of the type mentioned, it was customary to insert the molybdenum liner within a steel end cup by forging, which assembly, after heat treatment, was then fastened to the liner proper. The completed assembly was then inserted in the steel barrel. This resulted in a firm anchorage between the barrel and liner at this time, but the subsequent treatment at high temperature to develop required properties of the molybdenum since it occurred after insertion of the molybdenum liner in the end cup, but prior to the assembly of the complete liner, softened or annealed the steel so that rehardening of the cap was necessary, However, this subsequent rehardening procedure required high temperatures which damaged the quality of the molybdenum and resulted in an expansion of the steel, due to the martensite transformation and which loosened the previously-existing firm bond between the liner and anchor cap. Since the heat treatment to reharden the steel took place at the breech end of the barrel, where the liner is most severely stressed by the high temperatures and pressures developed in firing, the resulting deterioration of the liner and its bond to the barrel at this point, was particularly serious.

It is the principal object of the present invention to provide a method or process which avoids the drawbacks of the prior art as enumerated in the preceding paragraphs and a barrel of the type mentioned wherein the liner and barrel are firmly united while maintaining the previously-existing high quality of the metal of the liner.

It is another object of the invention to provide a gun barrel having a liner of a wear-resisting metal or alloy which is firmly anchored or secured to the barrel proper and in which the liner retains all the desired qualities of long life and resistance to e deterioration at the sustained high temperatures encountered in use in the field.

The specific nature of the invention as well as other objects and advantages thereof, will clearly appear from the accompanying drawings in which,

FIG. 1 is an exploded view in longitudinal section illustrating the component parts of the gun barrel, liner and securing members;

FIG. 2 is a longitudinal section showing the position of the parts of FIG. 1 in assembled relation; and

FIG. 3 is a cross section taken along plane 3-3 of FIG. 1.

Referring more particularly to the'drawing, wherein like reference characters designate like or corresponding parts throughout the different views, '1 indicates generally the breech end of a gun barrel having'a bore 2 therein. The barrel 1 is machined at its breech end to provide a reduced portion 3 which is externally threaded as at 4 and which terminates at its forward end at annular shoulder 1a. A liner indicated generally by 5 is provided to be fitted into the machined bore 2 and is composed of a series of identical composite rings, generally indicated by 6. Each ring consists of an outer steel ring 7 and an inner ring of molybdenum or molybdenum alloy 8 secured together. Rings 6 are placed coaxially in end to end relation and are welded together as at 9 to form a continuous tube or liner. As will be noted from FIGS. I and 2 the liner is assembled within tube 1 so that the rearward section projects from the breech end of the barrel a substantial distance, shown as a little more than one half the length of a section or ring of the liner.

The means for securing the barrel liner 5 within the barrel bore 2 includes a tubular steel end cap generally indicated at 10.

This cap is formed to define an enlarged annular forward portion 11 having an outer diameter equal to the corresponding diameter of the threaded end 4 of barrel 1, an inner diame ter a few thousandths of an inch less than the external diameter of the liner, and a dimension in the axial direction equal to the distance liner 5 projects rearwardly beyond the end of the barrel. The smaller bore of the cap'h'as a diameter the same as the internal diameter of the liner and its rearward end is reduced as at 10b to define a shoulder 13.

A clamping nut or sleeve 14 is threaded at it s forward end as at 16 with threads of the same pitch, but a few thousandths less in diameter than the corresponding diameter of v the threads 4 of barrel 1. The dimension in the axial direction of the threaded portion of the sleeve is the same as the corresponding threaded portion of barrel 1 and is followed by a smooth-bore having a dimension in the axial direction equal to the corresponding dimension of the enlarged portion of cap 10. Finally, the rearward end of nut 14 has a radially inwardly protruding flange 18 having dimensions in the axial and diametral directions equal to the corresponding dimensions of the end or anchoring cap 10. Complemental keyways 3a and 10a are formed in the contiguous ends of the barrel and cap, as clearly shown upon FIGS. 1 and 2, and, when the parts are in assembled relation receive a key 20, FIG. 2, with a snug fit.

In assembly, the liner 5 formed of the united rings 6 is then inserted into the machined bore 2 with the rearward end projecting, as shown in FIGS. 1 and 2.

This extension serves a dual purpose;' it increases the length of the erosion resistant surface, and it serves to anchor the liner within the barrel by means of end cap 10. The end cap is heated to approximately 300 C. and positioned over the protruding portion of the liner 5 with its front face abutting the end of barrel 1, the inner shoulder 19 abutting the end face of the liner 5 and, of course, with key recesses 30 and 10a in registration. As the cap shrinks on cooling, it grips the liner and provides a firm anchorage for connecting the same with the barrel.

The clamping nut 14 is then heated to approximately 300 C. and screwed on the barrel, and as in the case of the end cap, the close tolerances between threads 4 and 16 will provide a rigid connection between the barrel and liner when the nut cools and shrinks. The parts are thus rigidly and integrally united. Key 20 will, of course, be so sized as not to interfere with threading of nut 14 onto threads 4 and acts only to prevent rotation of the liner and cap relatively to the barrel. The gap between the nut 14 and the barrel 1 may be filled by a suitable member such as a two-piece annular ring 21 force fitted.

It is apparent from the foregoing specification that I have thus provided a lined barrel which attains all of the objects enumerated. The relatively low temperature used in shrinking the end cap 10 onto the protruding end of the liner and nut 14 onto the threaded end of the barrel, leave the quality of the metal of the liner and cap unaffected and thus assures that the liner is capable of withstanding erosion to the maximum extent at the point of greatest wear, namely at the beginning of the rifled area. Thus the steel end cap 10 and the liner 6 are treated separately until final assembly so that both can be heat-treated for optimum properties without detrimental effects on the other. By the construction shown wherein the end cap 10 and nut 14 are separate elements, the forward thrust produced by the hammering action of the gas seal (not shown) developed in firing, is borne by both the liner and the barrel rather than by the liner alone and a means provided for due to the construction shown, positively prevents backward movement of the liner. Due to the two-part construction, firing increases rather than decreases, the tension upon the threads of cap 14 with the result that there is no tendency for these threads to loosen. As one example, the nut 14 is machined so that each of its internal diameters is one thousandth of an inch less than the corresponding external dimension of cap and the liner has an external diameter two thousandths of an inch greater than the corresponding internal diameter of cap 10. The short distance mentioned in the claim may be about .312" for a barrel of about .75" caliber. The dimension given may be increased or decreased for barrels of proportionately larger or smaller Calibers.

While a preferred form of the invention has been shown and described, various modifications and substitutions of equivalents will occur to those skilled in the art after a study of the foregoing disclosure. Hence, the disclosures should be taken in an illustrative rather than a limiting sense, and it is the desire and intention to reserve all modifications within the scope of the subjoined claims.

lclaim:

1. In a lined gun barrel having a longitudinal bore and terminating at its breech end in a reduced coaxial externally threaded portion defining a rearwardly facing peripheral shoulder, a barrel liner comprising a continuous tube of identical composite rings concentrically joint joined in end to end relation to form a continuous tube having a smooth longitudinal bore, said tube adapted to be inserted in said longitudinal bore of said-barrel to a distance whereby a portion equal to substantially one-half halft'he length of one of said rings extends rearwardly of said gun barrel, each said ring including an outer ring of steel and an inner ring of molybdenum alloy, an end cap for said tube defining an enlarged forward portion and a reduced rearward portion forming a rearwardly facing shoulder, said forward portion having an enlarged bore equal in diameter to the external diameter of said barrel liner tube and an axial dimension equal to said extending portion of said liner, said rearward portion having a reduced bore equal in 

